This invention relates to optical torque sensors especially, but not exclusively, for incorporation in power-assisted steering systems for vehicles.
It is known to use electromagnetic torque sensors in power-assisted steering systems for vehicles which monitor magnetic flux or electric current, or other electromagnetic phenomena, but they are prone to interference form electrical and radio sources and need shielding to prevent spurious pulses in the control system. Electromagnetic shielding is difficult, heavy, and expensive. It has also been proposed to use emitters and sensors of electromagnetic radiation to detect torque in a torque sensor, however these can be difficult to calibrate and suffer from problems associated with changes over time in the output of the emitter and/or the sensitivity of the sensor.
An aim of the present invention is to provide a new relative angular displacement, or torque, sensor and/or a new power steering system.